A quantum-chemical study of pyridine adsorption on the surface of a charged mercury electrode

The interaction of a pyridine (Py) molecule with the surface of a charged mercury electrode was studied by the ab initio Hartree-Fock-Roothaan method. The electrode was modeled by a planar seven-atomic Hg-7 cluster with a sigma = +/- 12.5 muC/cm(2) surface charge density. The electronic properties of the [Hg-7(+/-). . . NC5H5] system were studied, the energy profiles of pyridine adsorption on the charged mercury surface were constructed, and the energies of adsorption were calculated. The dependence of the total energy of the adsorption system on the r(Hg-Py) distance is characterized by the deepest minimum if the charge density is positive and Py interacts with the metal through the lone pair on nitrogen. At a positive surface charge (sigma > 0), the vertical orientation of the adsorbate molecule is energetically favorable, whereas if the surface charge is negative (sigma < 0), adsorption does not occur.